In many surgical interventions, power-operated devices are used in modern days, which are able to perform or control specific works or movements. To mention an example, there is a surgical device for stabilizing or immobilizing a part of a moved tissue or also for the positioning of organs or surgical instruments and devices during an operation by means of a movable holding arm. Such a movable holding arm can be brought from its locked state into a movable state by means of compressed air. The control of the compressed air is achieved here by means of an electronic control system, which is supplied with the signals from actuation elements and sensors.
Furthermore, various instruments and devices have a two-part design, since on the one hand, one part of the device cannot be conditioned and sterilized due to the geometry, the employed materials or the like or is subject to such a high wear and tear that it is provided for single use only; or on the other hand, a further part of the device comprises components which are so expensive that a single use is not reasonable from the economic point of view.
The combination of this two-part design with a power-operated device or a device which is controlled by or operated with external energy results in various technical problems, which in turn result from the assembly and disassembly or the connection of the control or working equipment of both parts of the device.
In the mentioned example, it is necessary to connect two parts to each other, namely a technical unit enabling the power-operated locking of the movable holding arm, and the holding arm itself. Both parts of the device comprise an actuation element each, by means of which a slider can be moved in the technical unit. The actuation elements have the same function. Upon operating one of these actuation elements in the adapted state of the holding arm, the slider moves forward out of the housing against a compression spring. If the actuation elements are not operated, however, the slider is pressed rearward into the housing of the technical unit by spring force. Both actuation elements are implemented as a pushbutton. This is why the surgeon during use does not have to switch over between activating and deactivating the working procedure. The return of the slider and hence the locking of the holding arm occurs automatically by the spring force of the compression spring as soon as the actuation element is released.
The actuation elements are also required for assembling and disassembling the two parts: The actuation element provided on the technical unit makes the slider move forward, and then the holding arm can be adapted. If the actuation element is let go, the holding arm will be locked first. Subsequently, it is possible to work with the entire device and the two actuation elements. For disassembly, the actuation element of the technical unit is activated again, the slider is moved and the holding arm can be detached from the technical unit.
On the one hand, these procedures are not comfortable. As the actuation element is implemented as a pushbutton, it must not be released during the assembly or disassembly phase. If the electrical signal of the actuation element is interrupted, for instance due to the user performing a short unconscious movement during the assembly or disassembly phase, the slider immediately retracts into the housing of the technical unit. If the connection of the holding arm is not correctly adapted in the slider at that moment, it may happen that components of the technical unit or of the holding arm are damaged due to the return motion. If the user needed both hands for a short time during the assembly or disassembly phase, because something got jammed and the adaptation process is sluggish, this would not be possible for him as he must not let go of the actuation element.
On the other hand, the assembly and disassembly phases involve a considerable risk for the user. As long as he keeps the actuation element on the technical unit in the activated position with one hand, the slider is extended and is not covered any more by the housing. The slider has a geometry which is open toward the top, so that the adapting of the connection of the holding arm is made possible. A lateral insertion or other solutions for reducing the risk of this geometry seem to be impractical. By way of example, it may happen that the user puts his finger into said open geometry of the slider, if he discovers for instance some dirt in said adaptation site and wants to remove it. If he now released the actuation element, the slider would abruptly retract into the housing of the technical unit by means of the spring force. This may pose a high risk of injury for the user.
A technically comparable system is represented by the pneumatic bone punch according to DE 20 2004 015 643 U1. This device works pneumatically and consists of the handle piece comprising all technical devices which allow a power-operated functioning, and a punch shaft which has to be placed in the handle piece or adapted with it. With this system, a safety lever and an ON/OFF-switch are promoted which both reduce the risk of accidents resulting from such a power-operated system. The safety lever blocks the mechanism of the punch during cleaning the punch shaft, in other words if the user has to reach into the working area of the punch on purpose. This blocking is achieved in a purely mechanical fashion.
The ON/OFF switch is actually a pushbutton switch in the technical sense, activating the device in the pressed state and upon releasing the pushbutton automatically changing to the state “OFF” or “device inactive”. The ON/OFF switch additionally comprises a rotary switch which is installed so as to be hidden. By means of this additional switch, the main switch or main pushbutton can be blocked in order to prevent an unintentional operation of the device, for instance during placing it on an uneven underground, whereby the on-switch could be activated by the own weight of the device. This blocking is achieved in a mechanical manner, too.
The solutions which are supposed to allow safe working with the bone punch according to DE 20 2004 015 643 U1 need a sufficient installation space. The safety lever which has to absorb and withstand the full punching force and is constructed with a sufficient safety factor, cannot always be implemented in certain devices which likewise operate with high forces but have a substantially higher compactness. The larger disadvantage is, however, that this mechanism is not automatically in effect and may be forgotten.